BUDAPEST, Hungary — There's an easier way to see Europe than being crammed on a tourist bus or hustling hostels at the end of the day. A river cruise is one of the most relaxing and picturesque ways to view the wonders the continent, up close and personal.

While many cruise operators prowl the waterways, one of the most comprehensive is Viking Cruises, which boasts 19 ships (six more next year) and explores virtually every navigable river in Europe, parts of Asia and Africa.

Of these, the eight-day Danube cruise embarks in the historic city of Budapest, and weaves its way slowly down the green margins of the Danube, through flamboyant Vienna, fairy-tale towns like Germany's Regensburg, the lush vineyards of Austria and, finally, Hitler's favorite city, Nuremberg. (Or the reverse itinerary.)

The longships hold about 188 passengers, nothing like metropolis-sized seagoing cruise ships. Conviviality is the game here, where you can get to know almost everybody on board. Six land excursions to some of the most historic sites en route are included in the passage price. And they are something to behold.

Budapest — Hungary's capital — is divided by the Danube, with the mountainous Buda and its old city on the west and Pest, with its commercial district, on the east. At one time the two parts were connected only by a ferry, but now bridges transverse the gap, including the elegant suspension Chain Bridge, which is aglow with lights at night.

The chichi shopping district on Vaci Street, the Museum of Terror (once Nazi headquarters, which later housed the Communist police) and the righteously beautiful parliament building are part of the tour.

Stop by Heroes' Square, a site that saw the Hungarians' brave revolt against the Soviets.

From Gellert Hill you can view the Corot like-landscape of Budapest. The hill is named after St. Gellert, an Italian bishop who was executed here by placing him in a barrel studded with nails and rolling him into the Danube. (Anybody would deserve sainthood after that.)

Other sites include Matthias Church with its colorful ceramic roof, the 200-room Castle Palace and the multi-spas associated with the 30 mineral springs in Budapest.

Next stop: Vienna, the center of music and culture with the oldest Ferris wheel in the world, shouldering the sky at 213 feet. Vienna hosts almost 100 museums, ranging from doll collections to Freud's apartment. You'll also see the famous Spanish Riding School of Vienna where the Lippizan horses are trained, the Greek-inspired parliament and the central market stretching more than half a mile.

Famous for its dry sacher torte, the Hotel Sacher is where the treat originated. Exclusive shops populate Kohlmarkt Street and you can't miss St. Stephen's with its colorful tile roof, once the tallest tower in Europe.

Renowned for its composers — Strauss II, Mozart, Haydn, Beethoven, Schubert (the only one born here) — Vienna boasts a State Opera House that's booked every night. Part of the ship's optional excursions, for 59 Euros, includes an inspiring evening concert by the Vienna Residence Orchestra.

A side trip is available to Schonbrunn Palace, patterned after Versailles, the "country cottage" of the Hapsburgs. Maria Theresa, Marie Antoinette's mother, bore 16 children with her pasty-faced husband, Francis Stephen of Lorraine, and the brood visited in the summer. Schonbrunn Palace houses 1,441 rooms, with plenty of bedrooms for the randy couple.

Sitting onboard in your stateroom with its sliding glass doors, you can watch the countryside glide by and the most awe-inspiring of all the sites, Austria's Wachau Valley.

Here green vineyards scale the mountainside anchored by foothill villages that look like something out of Grimms' "Fairy Tales." The hamlets of Loiben, Durnstein (Richard the Lion-Hearted was imprisoned here) and Weissenkirchen are incredibly beautiful. Some of them retain their 16th century houses, and Weissenkirchen is still shrouded by the wall that encircled it in the 16th century.

Visits continue to Melk's 900-year old Benedictine Abbey with its library of 16,000 books, and on to Germany and Passau. Located at the confluence of three rivers, Passau houses the baroque St. Stephan's Cathedral and Europe's largest pipe organ, with 17,774 pipes, some as small as a needle. Every day at noon (except on Sundays, November to April) one of two organists in the village presents a recital that echoes off the stone pillars.

The medieval city of Regensburg (the Danube's oldest) is next, with its 12th century Old Stone Bridge, its town hall, the Gothic St. Peter's with its famous stained glass windows and houses that make you think you've been snagged in a time warp. Optional excursions to Weltenburg Abbey and the Danube Gorge are available.

The ship passes through 25 locks on this trek; most impressive is the Main Danube Canal on the way to Nuremburg, where it slides through 16 locks that lift the water to 1,330 feet.

Final stop is Nuremberg, once famous for its toys and crafts but now better known for the fascination it held for Hitler and as the site of post-war trials of Nazi officials. You can visit the impressive Documentation Center — located in the north end of the huge Congress Hall, which was built by the Nazis but never used.

Here are the Nazi Party Rally grounds seen in newsreels. Standing among the massive stonework, the stairs rising to the dais where Hitler ranted, one can almost hear the roar of the crowd.

In the Palace of Justice, visitors can stand where 21 Nazi war criminals were tried after Germany's defeat in World War II. A wall has been added to shorten the room and a crucifix now hangs above the judge's seat.

EXCURSIONS: Divided into robust and leisurely. The leisurely permits more time for photography.

AIR TRANSPORTATION: If you arrange your air travel through the cruise line, you might get a better value, as transfers, taxes, etc. are covered, with more than 165 gateways available.

TIPPING: Not mandatory in Austria. On the ship it's usually $10 per day per passenger.

FOOD: Cuisine onboard varies as you pass through each country, with specialties of that region emphasized. You don't want to miss the strudel, German sausages or Hungarian goulash. If you don't like any of that, you may have a steak or salmon every night. Wine is free with dinner and lunch.

TEMPERATURE: Hot in summer, cold in winter. The best time to visit is spring or fall, as the summer can be scorching.

The Royal Caribbean Quantum of the Seas was built at the Meyer Werft shipyards and delivered in October 2014. It's the first of two ships that have been part of the line's Project Sunshine. The sister ship Anthem of the Seas is due in spring 2015. Read about ship details